(a) Field of the Invention
The present invention relates to a thin film transistor array panel including a storage electrode.
(b) Description of the Related Art
Thin film transistors (TFTs) are used as switching elements for selectively transmitting voltages to be applied to pixels of display devices such as liquid crystal displays (LCDs) and electroluminescent (EL) displays.
The LCDs are one of the most widely used flat panel displays. An LCD includes two panels provided with field-generating electrodes and a liquid crystal (LC) layer interposed therebetween. The LCD displays images by applying voltages to the field-generating electrodes to generate an electric field in the LC layer, which determines orientations of LC molecules in the LC layer to adjust polarization of incident light.
Among LCDs including field-generating electrodes on respective panels, a kind of LCDs provides a plurality of pixel electrodes arranged in a matrix at one panel and a common electrode covering an entire surface of the other panel. The image display of the LCD is accomplished by applying individual voltages to the respective pixel electrodes. For the application of the individual voltages, a plurality of three-terminal (TFTs) are connected to the respective pixel electrodes, and a plurality of gate lines transmitting signals for controlling the TFTs and a plurality of data lines transmitting voltages to be applied to the pixel electrodes are provided on the panel.
A pixel electrode and a common electrode form a liquid crystal capacitor, which stores applied voltages after turn-off of the TFT. A storage capacitor, which is connected in parallel to the liquid crystal capacitor, is provided for enhancing the voltage storing capacity. The storage capacitor is usually implemented by overlap of the pixel electrode and a storage electrode provided on the panel.
The storage electrode has a configuration which gathers electrical charges in some places and it is called charge trapping. The charge trapping causes dark spots or horizontal lines on a screen of the LCD, thereby deteriorating image quality. The dark spots are generated when displaying middle grays, and the horizontal lines extend along the extending direction of the storage electrode because the charge trapping decreases the capacitance of the storage capacitors and thus obstruct the charging of the capacitors.